The motors currently used for these applications are brushed direct current (DC) motors, comprising a coiled rotor and a ferrite permanent magnet stator. The rotor is connected to a rotary collector. The current is injected via the brushes at the collector. This type of motor is commonly replaced with brushless motors, which operate without brushes. The latter include a coiled stator while the magnets are placed on the rotor. An electronic control system must provide the switching of the current in the stator windings.
This type of motor is used in particular in model aircraft, for DVD readers/burners or for small fans.
It is known in U.S. Pat. No. 4,556,809 to provide the rotor of an electric motor with discs provided with magnets intended to cooperate with a stator, extending in the form of a cylinder around the discs of the rotor. The thickness of the stator increases the radial width of the motor.
Application JP-A-2003/088068 describes an electric motor or dynamo comprising two rotor discs mounted on the same shaft, and between which is placed a set of bars each provided with a copper winding in order to form the stator. The permanent magnets are placed facing the windings on the surfaces of the rotor discs turned towards each other. The arrangement chosen aims to improve the complex method of producing windings, in particular the aforementioned cylindrical stator, and makes it possible to reduce production waste. A stacking of two structures one over the other makes it possible to produce a substantial quantity of electricity.
The structure shown in this document is not however adapted to be integrated into an actuating tube, these axial and radial dimensions are practically equivalent in the case of a simple structure. The stacking of two structures makes it possible to produce a motor that is more elongated but the objective of this stacking is not to reduce the radial dimensions, but to produce a more substantial quantity of energy.
It is known in DE-A-10 2006 038576 to longitudinally juxtapose, along a rotational axis of a rotor, the phases of an electric motor. This makes it possible to reduce its diameter but to the detriment of the length of the motor, as the latter is constituted of a succession of blocks each comprising a coil and the two corresponding bearings, in order to constitute each phase of the motor. Moreover, the coil being wound around a shaft of the rotor, the method of manufacture and assembly is complex.
The invention therefore proposes to improve the existing devices in order to define an electric motor structure dedicated to tubular actuators with the following objectives:                reduced dimensions, in particular with regards to the radial dimensions        improvement of the sound level        production of torque at a reduced speed with rotor inertia        facility of winding.        